ICSE Class 10 Physics 2019 Solved Paper
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Question : 49
Total: 74
A pendulum has a frequency of 4 vibrations per second. An observer starts the pendulum and fires a gun simultaneously. He hears the echo from the cliff after 6 vibrations of the pendulum. If the velocity of sound in air is 340 m ∕ s , find the distance between the cliff and the observer.
Solution:
Time taken for 4 vibrations of the pendulum = 1 s e c
Time taken for 1 vibrations of the pendulum=
s e c
∴ Time taken for 6 vibrations of the pendulum =
× 6 = 1.5 s e c
We know,
v =
ord =
∴ d =
= 255 m
Time taken for 1 vibrations of the pendulum
We know,
or
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